Abstract: Pretreatment of lignocellulosic materials is essential for bioconversion because of the various physical and chemical barriers that greatly inhibit their susceptibility to bioprocesses such as hydrolysis and fermentation. The aim of this article is to review some of the most important pretreatment methods developed to date to enhance the conversion of lignocellulosics. Steam explosion, which precludes the treatment of biomass with high-pressure steam under optimal conditions, is presented as the pretreatment method of choice and its mode of action on lignocellulosics is discussed. The optimal pretreatment conditions for a given plant biomass are defined as those in which the best substrate for hydrolysis is obtained with the least amount of soluble sugars lost to side reactions such as dehydration. Therefore, pretreatment optimization results from a compromise between two opposite trends because hemicellulose recovery in acid hydrolysates can only be maximized at lower pretreatment severities, whereas the development of substrate accessibility requires more drastic pretreatment conditions in which sugar losses are inevitable. To account for this heterogeneity, the importance of several process-oriented parameters is discussed in detail, such as the pretreatment temperature, residence time into the steam reactor, use of an acid catalyst, susceptibility of the pretreated biomass to bioconversion, and process design.

Abstract: In this study, the glycerol metabolism by Klebsiella pneumoniae is stoichiometrically analyzed according to energy (ATP), reducing equivalent and product balances. The theoretical analysis reveals that a microaerobic condition is more perfect for the production of 1,3-propanediol (1,3-PD) from glycerol by K. pneumoniae than anaerobic and aerobic conditions. The yields of 1,3-PD, biomass and ATP to glycerol under microaerobic conditions depend not only on the molar fraction of reducing equivalent oxidized completely by molecular oxygen in tricarboxylic acid (TCA) cycle (δ), but also on the molar fraction of TCA cycle in acetyl-CoA metabolism. The maximum theoretical yield of 1,3-PD to glycerol could reach to 0.85 mol/mol rather than 0.72 mol/mol if all acetyl-CoA entered into TCA cycle instead of acetic acid pathway under anaerobic conditions. The yield of 1,3-PD is still higher than 0.72 mol/mol in a range of δ between 0.11 and 0.48, which corresponds to respiratory quotient (RQ) between 11.34 and 2.66. In the same range of δ or RQ, the biomass under a microaerobic condition is more than that of an anaerobic culture. The experimental results of batch cultures demonstrate that microaerobic cultivations are favorable for cell growth, reduction of culture time and ethanol formation, and enhancement of volumetric productivity of 1,3-PD. In addition, no aeration could improve the yield of 1,3-PD to glycerol in comparison with that of an anaerobic or aerobic culture.

Abstract: Apple production in the world has increased significantly over the last 10 years. A considerable fraction of these fruits, mainly those not approved for fresh consumption, is industrially processed to produce juices, flavours and concentrates. During this processing, a large amount of solid residues is produced, comprised mainly of peels, seeds, and pulp, which are collectively known as ‘apple pomace’. This work aims to select biological treatments and conditions for the bioconversion of apple pomace by Candida utilis and Pleurotus ostreatus, either individually or sequentially, into an enriched substrate with increased digestibility for use as ruminant feed. After C. utilis fermentation, the protein level increased 100% and the mineral content 60%, accompanied by 8.2% of increase in the digestibility. The level of free sugars decreased 97% after substrate supplementation with ammonium sulphate (10 g l−1). After optimization, sequential fermentation with C. utilis and P. ostreatus achieved a high protein level with 500% of crude protein enrichment after 60 days of fermentation as well as a considerable increase in the mineral level. The level of free sugars increased after the fermentation with P. ostreatus alone due to pectin and hemicellulose degradation. Considering the time required for fermentation, the C. utilis treatment was the most efficient treatment to convert apple pomace into a more nutritive substrate for ruminant feed.

Abstract: The present invention provides means for the production of desired end-products of in vitro and/or in vivo bioconversion of biomass-based feed stock substrates, including but not limited to such materials as starch and cellulose. In particularly preferred embodiments, the methods of the present invention do not require gelatinization and/or liquefaction of the substrate.

Abstract: Streptomyces sp. Y-110, isolated from soil, modified compactin to pravastatin, a therapeutic agent for hypercholesterolemia. In a batch culture, the highest production of pravastatin was 340 mg l−1 from 750 mg compactin l−1 in 24 h. By intermittent feeding of compactin into the culture medium, both the compactin concentration and its conversion increased to 2000 mg l−1 and 1000 mg pravastatin l−1, respectively, with the conversion rate of 10 mg l−1 h−1. Continuous feeding of compactin increased production of pravastatin to 15 mg l−1 h−1.

Abstract: Aims: To investigate the production of xylitol by the yeast Candida guilliermondii FTI 20037, in a bioreactor, from rice straw hemicellulosic hydrolysate with a high xylose concentration. Methods and Results: Batch fermentation was carried out with rice straw hemicellulosic hydrolysate containing about 85 g xylose l−1, in a stirred-tank bioreactor at 30°C, under aeration of 1·3 vvm (volume of air per volume of medium per min) and different stirring rates (200, 300 and 500 rev min−1). The bioconversion of xylose into xylitol by the yeast depended on the stirring rate, the maximum xylitol yield (YP/S = 0·84 g g−1) being achieved at 300 rev min−1, with no need to pretreat the hydrolysate for purification. Conclusions: To determine the most adequate oxygen transfer rate is fundamental to improving the xylose-to-xylitol bioconversion by C. guilliermondii. Significance and Impact of the Study: For the microbial production of xylitol to be economically viable, the initial concentration of xylose in the lignocellulosic hydrolysate should be as high as possible, as with high substrate concentrations it is possible to increase the final product concentration. Nevertheless, there are few reports on the use of high xylose concentrations. Considering a process in bioreactor, from rice straw hemicellulosic hydrolysate, this is an innovator work.

Abstract: The bioconversion of L-phenylalanine to 2-phenylethanol by Saccharomyces cerevisiae in fed-batch experiments has shown that concentrations of 2-phenylethanol of >2.9 g/L have a negative impact on the oxidative capacity of the yeast. Without tight control on ethanol production, and hence on the feed rate, ethanol rapidly accumulates in the culture media, resulting in complete inhibition of cell growth before the maximal 2-phenylethanol concentration of 3.8 g/L, obtained in the absence of ethanol production, could be achieved. This effect was attributed to a cumulative effect of ethanol and 2-phenylethanol, which reduced the tolerance of the cells for these two products. To enhance the productivity of the bioconversion, a novel in situ product recovery strategy, based on the entrapment of an organic solvent (dibutylsebacate) into a polymeric matrix of polyethylene to form a highly absorbent and chemically and mechanically stable composite resin, was developed. Immobilization of the organic solvent successfully prevented phase toxicity of the solvent and allowed for an efficient removal of 2-phenylethanol from the bioreactor without the need for prior cell separation. The use of the composite resin increased the volumetric productivity of 2-phenylethanol by a factor 2 and significantly facilitated downstream processing, because no stable emulsion was formed. The 2-phenylethanol could be backextracted from the composite resin, yielding a concentrated and almost cell-free solution. In comparison to two-phase extractive fermentations with cells immobilized in alginate-reinforced chitosan beads, the use of a composite resin was extremely inexpensive and simple. In addition, the composite resin was found to be insensitive to abrasion and chemically stable, such that sterilization with 2 M NaOH or heat was possible. Finally, the composite resin could be produced on a large scale using commercially available equipment.

Abstract: The present invention provides means for the production of desired end-products of in vitro and/or in vivo bioconversion of biomass-based feed stock substrates, including but not limited to such materials as starch and cellulose. In particularly preferred embodiments, the methods of the present invention do not require gelatinization and/or liquefaction of the substrate. In particularly preferred embodiments, the present invention provides means for the production of ethanol.

Abstract: Fermented succulent shoots of bamboo (Bambusa balcooa and Dendrocalamus strictus) are an enriched source of phytosterol. Microorganisms from the 'soibum exudate' involved in microbial bioconversion of phytosterol during fermentation of succulent bamboo shoots were isolated and identified as Bacillus subtilis, B. licheniformis, B. coagulans and Micrococcus luteus. Crude phytosterol was purified to isolate β-sitosterol by thin layer chromatography and identified by IR and mass spectral data. The isolated β-sitosterol was then subjected to microbial bioconversion using B. subtilis yielding a considerable amount of androstadienedione in the presence of metal chelate inhibitor (0.1 % a, a'-dipyridyl).

Abstract: In this study we constructed an artificial flavohemoprotein by fusing Vitreoscilla hemoglobin (VHb) with D-amino acid oxidase (DAO) of Rhodotorula gracilis to determine whether bacterial hemoglobin can be used as an oxygen donor to immobilized flavoenzyme. This chimeric enzyme significantly enhanced DAO activity and stability in the bioconversion process of cephalosporin C. In a 200-mL bioreactor, the catalytic efficiency of immobilized VHb-DAO against cephalosporin C was 12.5-fold higher than that of immobilized DAO, and the operational stability of the immobilized VHb-DAO was approximately threefold better than that of the immobilized DAO. In the scaled-up bioprocess with a 5-L bioreactor, immobilized VHb-DAO (2500 U/L) resulted in 99% bioconversion of 120 mM cephalosporin C within 60 min at an oxygen flow rate of 0.2 (v/v) x min. Ninety percent of the initial activity of immobilized VHb-DAO could be maintained at up to 50 cycles of the enzymatic reaction without exogenous addition of H(2)O(2) and flavin adenine dinucleotide (FAD). The purity of the final product, glutaryl-7-aminocephalosporanic acid, was confirmed to be 99.77% by high-performance liquid chromatography (HPLC) analysis. Relative specificity of immobilized VHb-DAO on D-alpha-aminoadipic acid, a precursor in cephalosporin C biosynthesis, increased twofold, compared with that of immobilized DAO, suggesting that conformational modification of the VHb-DAO fusion protein may be altered in favor of cephalosporin C.

Abstract: Batch production of xylitol from the hydrolysate of wheat straw hemicellulose using Candida guilliermondii was carried out in a stirred tank reactor (agitation speed of 300 rpm, aeration rate of 0.6 vvm and initial cell concentration of 0.5 g l(-1)). After 54 h, xylitol production from 30.5 g xylose l(-1) reached 27.5 g l(-1), resulting in a xylose-to-xylitol bioconversion yield of 0.9 g g(-1) and a productivity of 0.5 g l(-1) h(-1).

Abstract: The anaerobic bioconversion of solid poultry slaughterhouse wastes was kinetically investigated. The modified version of simulation model was applied for description of experimental data in mesophilic laboratory digester and assays. Additionally, stages of formation and consumption of long chain fatty acids (LCFA) were included in the model. Batch data on volatile solids, ammonium, acetate, butyrate, propionate, LCFA concentrations, pH level, cumulative volume, and methane partial pressure were used for model calibration. As a reference, the model was used to describe digestion of solid sorted household waste. Simulation results showed that an inhibition of polymer hydrolysis by volatile fatty acids and acetogenesis by NH3 or LCFA could be responsible for the complex system dynamics during degradation of lipid- and protein-rich wastes.

Abstract: The invention relates to a method for processing organic material, in which method bioconversion is performed on the organic material in at least one first reactor, the biogas formed in the bioconversion is treated with ammonia in the at least one second reactor and buffer solution produced in the second reactor is recycled to the bioconversion in the first reactor. Thus the carbon dioxide of the mixed methane/carbon dioxide gas reacts with the ammonia and forms a buffer compound, such as ammonium bicarbonate and/or ammonium carbonate.

Abstract: Lactobacillus reuteri was immobilized on silica gel to evaluate the bioconversion of linoleic acid (LA) into conjugated linoleic acid (CLA), consisting of cis-9,trans-11 and trans-10,cis-12 isomers. The amount of cell to carrier, the reaction time, and the substrate concentration, pH, and temperature for CLA production were optimized at 10 mg of cells/(g of carrier), 1 h, 500 mg/L LA, 10.5, and 55 degrees C, respectively. In the presence of 1.0 mM Cu(2+), CLA production increased by 110%. Under the optimal conditions, the immobilized cells produced 175 mg/L CLA from 500 mg/L LA for 1 h with a productivity of 175 mg/(L.h) and accumulated 5.5 times more CLA than that obtained from bioconversion by free washed cells. The CLA-producing ability of reused cells was investigated over five reuse reactions and was maximal at pH 7.5, 25 degrees C, and 1.0 mM Cu(2+). The total amount of CLA by the combined five reuse reactions was 344 mg of CLA/L reaction volume. This was 8.6 times higher than the amount obtained from reuse reactions by free washed cells.

Abstract: The main aim of this work was to intensify conventional composting of a mixture of sewage sludge and solid food wastes by a one-stage thermophilic bioconversion of these wastes into an organic fertilizer. An intensive process was carried out in a closed system, with or without addition of a starter culture of Bacillus thermoamylovorans. The most effective thermophilic bioconversion of the mixture of food waste and sewage sludge, with addition of starter culture, was when the pH was buffered with calcium carbonate, or the pH drop in the material was prevented by preliminary removal of sulphides from sewage sludge by hydrogen peroxide.

Abstract: The evaluation of cheap carbon sources (co-substrate) and process conditions for microbial treatment of domestic wastewater sludge (DWS) was investigated using a liquid state bioconversion (LSB) la...

Abstract: Platinum mines produce large amounts (750 m3 per month) of woodchips as by-product during ore extraction, posing environmental hazards but also a possible source of organic material to be applied in revegetating tailing dams. The aims of this study were to assess the effectiveness of different bioconversion strategies viz. composting, vermicomposting and a commercial micro-organism inoculant (EM). Woodchips (WC) and sewage sludge (SS) with a mixing ratio of 3:1 were composted and vermicomposted for 112 days and the generated products evaluated in terms of their chemical and physical characteristics. Despite low temperatures (33 °C) in all the treatments, no Escherichia coli or Salmonella was detected in any of the end-products. No significant (P ≥ 0.05) difference in the mean percentage change of C in the different bioconversion strategies was observed and it was only in the SS+WC and SS+WC+EM groups that the soil available P (P-Bray 1) increase was statistically significant (P ≤ 0.05). Treatments containing SS showed significant (P ≤ 0.05) decreases in NH4 +, whereas NO2 - and NO3 -increased significantly (P ≤ 0.05). The NH4 +:NO3 - ratios in the treatments containing SS were lower than 0.16, ranging from 0.011-0.0016, which is an indication of the maturity of the compost. Total solids and ash contents showed an increase, while the volatile solids and the lignin decreased, but it was only in the vermicomposted treatments that these changes were statistically significant (P ≤ 0.05). The percentage neutral detergent fibre (%NDF) and %cellulose decreased significantly (P ≤ 0.05) in all the treatments containing SS and particle size analysis indicated higher reductions in the vermicomposted treatments. It is concluded that vermicomposting of industrially produced woodchips and sewage sludge is more effective than composting and that the addition of a microbial inoculant did not have a significant effect on the decomposition process.

Abstract: We examined the performance of Streptomyces lividans strain W25 containing a hybrid expandase (deacetoxycephalosporin C synthase; DAOCS) gene, obtained by in vivo recombination between the expandase genes of S. clavuligerus and Nocardia lactamdurans for resting-cell bioconversion of penicillin G to deacetoxycephalosporin G. Strain W25 carried out a much more effective level of bioconversion than the previously used strain, S. clavuligerus NP1. The two strains also differed in the concentrations of FeSO4 and α-ketoglutarate giving maximal activity. Whereas NP1 preferred 1.8 mM FeSO4 and 1.3 mM α-ketoglutarate, recombinant W25 performed best at 0.45 mM FeSO4 and 1.9 mM α-ketoglutarate.

Abstract: Pseudomonas aeruginosa strain PR3 (NRRL B-18602) converts oleic acid to a novel compound, 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) The bioconversion was scaled up in a 7-l bench-top, stirred-batch reactor to produce DOD for testing of potential industrial uses Aeration was supplied continuously from the top through two ports on the headplate and periodically through a bottom sparger, in conjunction with the use of marine impellers for agitation This unique aeration arrangement maintained the dissolved O2 concentration in the 40-60% range during the period of maximal bioconversion and it also avoided excessive medium foaming during the reaction Furthermore, the level of dissolved O2 in the first 24 h of reaction played an important role in the initial rate of DOD production DOD production reached a plateau after 72 h with a yield up to 100 g (or 50% recovery) from a total of 9 l medium from two reactors run simultaneously The final culture broth was processed using newly adapted procedures in the pilot plant that included crystallization of DOD from ethyl acetate solution at -15 degrees C The newly developed bioprocess will serve as a platform for the scale-up production of other value-added products derived from vegetable oils and their component fatty acids

Abstract: Candida guilliermondii fermented a eucalyptus hemicellulosic hydrolysate that had been treated with calcium oxide, phosphoric acid and activated charcoal. The influences of different xylose and ammonium sulfate concentrations on the production of xylitol were studied. A response surface was obtained with value R 2 >0.97 and p<0.01. The model estimated a maximum xylitol production of 20.82 g/dm 3 in the culture medium supplemented with ammonium sulfate (1.8 g/dm 3 ) and xylose (45.5 g/dm 3 ).